Before you read this, think of it this way your 82-87 325,e,es has the 2.7L 9.0:1 compression M20 and the 87-92 325i,is,ix have the high performance 2.5L 8.5:1 compression M20. Now if you have both an e and an i then take all of the high performance i parts off and bolt them on to the e and you will have a high performance, high torque 9.0:1 compression 2.7L M20. This is the quick way. The long way is putting on the i head which is not necessary for this quick performance upgrade.

Now if you have an i car then I am going to suggest getting any 2.7 crank and use your i rods and buy custom pistons that already have valve reliefs cut in them and at a compression of your choice.

For 87-92 325i,is,ix,ic~2.5L modelE30 You already have 1.1/1.3 Motronic all you need is 173ecu. To build a 2.7i you will need 2.7 crank, rods, pistons(eta,seta)

Parts Needed:
i intake manifold, i throttle body, i injectors, i AFM(air fuel module), i FPR(fuel pressure regulator 3.0bar), all i pulleys(fan, water pump, crankshaft), i belts, i thermostat housing, i 173ecu(computer in glove box), all 1.1/1.3 Motronic harness and sensors, spark plug wires

Optional Parts:
i double valve springs, i valve cover, i duel exhaust, i radiator and expansion tank, i single fuel pump fuel tank and fuel lines, i flywheel, i transmission with drive-shaft(Must use original center support bearing), i differential(4.10 from ix), i brake booster, i 90amp alternator

1987 325,e,es
Note: In 1987 some e30 are equip with 1.1 Motronic sensors and harness and have the i pulleys and thermostat housing.

Parts Needed:
i intake manifold, i throttle body, i injectors, i AFM(air fuel module), i FPR(fuel pressure regulator 3.0bar), all i pulleys(fan, water pump, crankshaft), i belts, i thermostat housing, i 173ecu(computer in glove box), all 1.1/1.3 Motronic harness and sensors, spark plug wires

Optional Parts:
i double valve springs, i valve cover, i duel exhaust, i radiator and expansion tank, i single fuel pump fuel tank and fuel lines, i flywheel, i transmission with drive-shaft(Must use original center support bearing), i differential(4.10 from ix), i brake booster, i 90amp alternator[U]
1988 super eta, seta

Parts Needed:
i intake manifold, i 173ecu(computer in glove box)

Optional Parts:
i cam, i double valve springs, i duel exhaust, i radiator and expansion tank, i single fuel pump fuel tank and fuel lines, i flywheel, i transmission with drive-shaft(Must use original center support bearing), i differential(4.10 from ix), i brake booster, i 90amp alternator[U]

i head with eta pistons 8.4:1 compression good torque good acceleration, best for turbo applications and engine management

i head with seta pistons 8.5:1 compression great torque great acceleration

i head with i rods and custom pistons 10.0:1 compression better torque excellent acceleration

Notes

Note 1: Once 1.3 Moronic is swapped in you will rev past 5300rpm so you will need to install the 7000rpm i tachometer

Note 2: Double valve springs are preferred for high rev applications but you can run the stock 86 single valve springs under 5300rpms until you are ready to take the head off.

Note 3: A 30amp fuse will be needed in the fuse box for the fuel pump.

Note 4:1.3 Motronic wire harness is larger then 1.0basic Motronic harness so the inlet hole on the firewall passenger side will need to be slightly enlarged.

Note 5: None of the i parts will increase your rev limit (5300rpm) without the 173ecu 1.3 Motronic up-grade(6300rpm) and for 7000+ rev limit try out various performance chips.

Note 6: After upgrading to 1.3 Motronic you may want to move your power curve up, so try the i cam or bigger in the eta head. The eta head will need to have oil passages drilled for the 3 extra cam journals at a knowledgeable machine shop so you can put the 7 bearing i cam or bigger in the eta head.

Note 7: The 1988 325,e,es 2.7 (super eta, seta) which is the only year with 2.7 domed pistons that mate with the i head and have proper compression for NA applications.

Note 9: The i rods are longer then the e rods and will rev better because of the rod ratio. This combination is better then the stock parts combination but consists of custom pistons.

Note 10: If you want a better rod ratio or cant find the 88 super eta pistons then go with custom non-interference pistons that will work with (e crank, i rods, i head).

Note 11: If Turbo is in mind use (e Crank, e rods, e pistons, i head).
Because the i head has domed combustion chambers unlike the eta head which has flat combustion chambers, the matching of the eta flat top piston and the domed chamber of the i head will result in lower compression (which is perfect for turbo applications). The i head will bolt right on to the stock eta bottom end with no machining needed. The only problem is rough idle and hard start, which can be fixed with advanced engine management like MS,MS2,MMS or a custom chip.

Note 12: Here is quote from Wikipedia.com supporting the 2.7i and explaining the 1.3 upgrade.

For the 1988 model year, the eta cars got a refresh from the factory. This included a newer Bosch Motronic version with adaptive idle control, a 325i head casting with the larger valves, ports, revised combustion chambers and water jacket, new pistons to fit the 2.7 L stroke with the 2.5 L head, a dual exhaust system and a 5300 RPM rev limit. Though it only made slightly more power in stock form, it could be easily boosted by bolting on a 325i head, a complete 325i intake manifold and throttle and plugging in the 325i engine control unit. Depending on which cam, chip and intake is used, the combination can make over 180 horsepower with the stock compression ratio.
In aftermarket modifications that are inspired by custom versions of Alpina and AC Schnitzer, the long-stroke eta engine block is often combined with a 325i head to a so-called 327i that combines the high low-rev torque of the eta with the top-range power of the 325i.

so is it safe to just run the computer from the i on the e engine as long as you dont over rev it?

The i computer only connects to the 1.1 and 1.3 Motronic wire harness, so you must swap all i related parts on to the eta motor for the i computer to work.

Once 1.3 Motronic is installed your red line will be higher then the eta valve springs can handle so if you plan on revving past 5300rpm i double valve springs are suggested to eliminate valve float and possible valve spring breakage.

I ran single valve spring in my 2.7i until I was ready to install the i cam, i valve springs, head gasket, and drill 3 extra oil passages in the eta head for the i cam.

So don't plan on revving past 5300rpms with single valve springs unless you want to break something.

whats the advantage in the upgrade? better fuel economy? power? and i wish i could find a $100 325i car around here lol

thanks

What you are doing is making an old m20 82-87 newer with updated electronics, intake and fuel system.

All eta engines used Bosch Motronic engine management systems that were calibrated for maximum fuel economy. The result was a very conservative spark advance curve and fuel delivery curve. In addition, the Motronic had a built-in rev limiter that engaged at about 4750 rpm. This very low redline was the result of the four bearing cam, soft valve springs, intake manifold and camshaft design. Due to the very low overlap and short duration of the cam and the intake manifold tuning, the motor does not make any power over about 5,000 RPM.

For the 1988 model year, the eta cars got a refresh from the factory with Bosch Motronic 1.1/1.3 Adaptive fuel injection a modification that adjusts the idle speed of a cold engine and a 6200 redline.

here are a couple quick engine piscs. nice and dirty for ya. id like to do this to my car. but its not going to happen till the start of the new year. it eases my mind that i wont have to hack the harness at all.

Well, since I have built several of these set-ups i guess i can post my results here. I started off with no real info or support of the eta 2.7i build. I started with my 350k mile m20b27. I have built 2 eta heads. Both used I cams, I also used a 274 regrind, and a 283 catcam.

Both heads were ported on the intake and exhaust. I have found that enlarging the intake to i head inlet specs is a waste because the volume of air coming in is bottlenecked by the smaller valves. Mid range torque jumped with the bigger ports, but top end seemed to die out over 5k. My previous head had a less extensive port job and made very linear power. I had both of these heads on my m20. I used m20b25 springs and drilled the cam journals for the 7 bearing cam.

Out of all the cams I tried, I feel the most worthwhile for a small valve eta head is the I cam. The 274 was okay, but lacked low end punch, and the 283 was another waste as the car never felt like it was ever in a powerband even at 6k+. Needless to say that cam was swapped out quickly, yet made its way back into the same head after I sold it, and I still think its holding that car back.

As far as components I used, I went with the 325i intake, throttle body, exhaust, and complete motronic 1.3 (no chip). The car was quick for what it was even with 2.93 gears it would run. I swapped in a 3.25lsd and it would max out around 140 on a flat road. 0-60 times were probably in the mid 7s and it was about as quick as an svt focus and stock civic si.

You do not need to swap all of the parts listed in the first post. The coils are universal, (im still using my original fuel pumps even with my m50), the exhaust manifolds are almost identical. The only things you really need are:
AFM
TPS
FPR
thermostat housing with all sensors (only 2)
crank position sensor with reluctor wheel (front crank pulley)
spark plug wires for the pick-up on wire #6
injectors
ICV
and thats about it if i remember.

When my m20 kicked the bucket from the high mileage and high rpm running, I parted it out and sold 2 'kits' made up of the heads I built and 2 complete motronic conversions. Both cars are still running and if I may say so are complete beasts. One belongs to e30_325es on here and e30tech, the other belongs to cowden_12 on here.

e30_325es's car now has a mark D chip, 283 cam, m30 afm, bav auto headers full exhaust, fan delete, 8mm wires, and a 3.73lsd. He put down 146hp/146 torque (i believe torque is so low because of the 283 cam). His car ran a 15.4 before he blew the small case 4.10

cowden_12's car is an 84 318 with full m20b27 swap, motronic 1.1 with jim C chip, turner intake, single 2 inch exhaust with no cat and magnaflow muffler, 325i flywheel, small case 3.91. His car feels stronger than e30_325es's and I think it will run with my m50.

Both cars are running proof that high performance from an eta is possible. Also look at rs4pro's car who has the same set-up, now with an mas air conversion and a supercharger. I hope to shed confusion on this subject well into the future, as there are becoming more and more threads asking questions that have already been answered in the past. Yes, it has been done, and has been proven.

You do not need to swap all of the parts listed in the first post. The coils are universal, (im still using my original fuel pumps even with my m50), the exhaust manifolds are almost identical. The only things you really need are:
AFM
TPS
FPR
thermostat housing with all sensors (only 2)
crank position sensor with reluctor wheel (front crank pulley)
spark plug wires for the pick-up on wire #6
injectors
ICV
and thats about it if i remember.

Etasport Thank you for your post! I have been looking for more insight.
(thanks for the advice on cams)

Etasport is right about what you need to upgrade to run a i ecu.

I was emphasizing on a total i 1.3 upgrade.

Your experiences with cams have all been on 82-87 eta flat top piston heads right? If So have you put an i head on your flat top pistons?